Design of photoactive ruthenium complexes to study electron transfer and proton pumping in cytochrome oxidase

► A variety of ruthenium based flash photolysis schemes are described. ► Rate of electron transfer between cytochrome c and cytochrome oxidase is measured. ► Binding domain between cytochrome c and cytochrome c oxidase is defined. ► Rate of electron transfer between CuA and heme a is measured. ► Rate of electron transfer between heme a and heme a3/CuB is measured.